DOCSLIB.ORG

Complex Bifurcation Structures in the Hindmarsh–Rose Neuron Model

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Complex Bifurcation Structures in the Hindmarsh–Rose Neuron Model International Journal of Bifurcation and Chaos, Vol. 17, No. 9 (2007) 3071–3083 c World Scientific Publishing Company COMPLEX BIFURCATION STRUCTURES IN THE HINDMARSH–ROSE NEURON MODEL J. M. GONZALEZ-MIRANDA´ Departamento de F´ısica Fundamental, Universidad de Barcelona, Avenida Diagonal 647, Barcelona 08028, Spain Received June 12, 2006; Revised October 25, 2006 The results of a study of the bifurcation diagram of the Hindmarsh–Rose neuron model in a two-dimensional parameter space are reported. This diagram shows the existence and extent of complex bifurcation structures that might be useful to understand the mechanisms used by the neurons to encode information and give rapid responses to stimulus. Moreover, the information contained in this phase diagram provides a background to develop our understanding of the dynamics of interacting neurons. Keywords: Neuronal dynamics; neuronal coding; deterministic chaos; bifurcation diagram. 1. Introduction 1961] has proven to give a good qualitative descrip- There are two main problems in neuroscience whose tion of the dynamics of the membrane potential of solution is linked to the research in nonlinear a single neuron, which is the most relevant experi- dynamics and chaos. One is the problem of inte- mental output of the neuron dynamics. Because of grated behavior of the nervous system [Varela et al., the enormous development that the field of dynam- 2001], which deals with the understanding of the ical systems and chaos has undergone in the last mechanisms that allow the different parts and units thirty years [Hirsch et al., 2004; Ott, 2002], the of the nervous system to work together, and appears study of meaningful mathematical systems like the related to the synchronization of nonlinear dynami- Hindmarsh–Rose model have acquired new interest cal oscillators. The other is the neural coding prob- [Holmes, 2005] because of the new information that can now be obtained from them. Int. J. Bifurcation Chaos 2007.17:3071-3083. Downloaded from www.worldscientific.com lem [Sejnowski, 1995; Abeles, 2004], which is aimed to know how the neurons encode the information In particular, it has been found recently that that they transmit and exchange in the working the dynamics of this system, when studied as a of the nervous system, and is related to both, the function of significant control parameters, presents knowledge of the different types of dynamics avail- two relevant features: (i) continuous interior cri- able to nonlinear dynamical systems and to chaos sis [Gonz´alez-Miranda, 2003], which are abrupt synchronization. changes in the nature of the dynamics of the sys- The theoretical study of such problems, in its tem attractor, and (ii) block structured dynamics by SOUTH CHINA UNIVERSITY OF TECHNOLOGY on 01/01/19. Re-use and distribution is strictly not permitted, except for Open Access articles. most basic aspects, partly relies on mathematical [Gonz´alez-Miranda, 2005], which is a complex bifur- models of the electrophysics of a single neuron, cation structure where the dynamics available to the most of them developed from the pioneering work system are grouped in blocks of alike periodicity. by Hodgkin and Huxley [1952]. Among them, the The first of these items provides a potential mech- model by Hindmarsh and Rose [1984], which is the anism for rapid responses in the nervous system result of a mapping of the Hodgkin–Huxley model by switching between different dynamical behav- to a relatively simple nonlinear oscillator [Fitzhugh, iors. The second provides structures that appear as 3071 3072 J. M. Gonz´alez-Miranda possible basic elements to encode messages in the 1.5 apparently random trains of action potentials that x run along the axon of an activated neuron. 0 -1.5 These two phenomena have received detailed study at particular restricted values of the 1.5 Hindmarsh–Rose model parameters. The aim of the x 0 present paper is to report a comprehensive study of -1.5 the manifestation of these phenomena for a wide 1.5 range of system parameters; that is, to provide x 0 a phase diagram of the Hindmarsh–Rose model, -1.5 which gives a global view of the availability of these 1.5 and other dynamical behaviors to this system. x This article is arranged as follows. After this 0 introduction, in Sec. 2, we give a basic description -1.5 of the complexities in the bifurcation diagrams of 1.5 the Hindmarsh–Rose neuron model. In Sec. 3, we x 0 present the results of a linear stability analysis in a -1.5 wide and significant region of the parameter space. 1.5 In Sec. 4, we analyze stability from the nonlinear x 0 point of view by means of the use of Lyapunov -1.5 exponents, and go further in the nonlinear analy- 1.5 sis giving a global view of the bifurcation diagrams. x In Sec. 5, we provide evidence for the structural sta- 0 bility of the above results, and finally, in Sec. 6 we -1.5 0 200 400 600 800 1000 1200 discuss and summarize the main conclusions of the t paper. Fig. 1. Time series for the action potential for the Hindmarsh–Rose model for r =0.003 and different values of 2. Complex Bifurcation Structures the current applied: (a) I =1.26, (b) I =1.28, (c) I =1.67, (d) I =3.20, (e) I =3.29, (f) I =3.34, and (g) I =3.50. The Hindmarsh–Rose model describes the dynam- ics of the membrane potential in the axon of a neu- ron, x(t), by means of a three-dimensional system oscillatory solutions than can be simple periodic fir- of nonlinear first-order differential equations, which ings of a single spike [Figs. 1(b) and 1(g)], periodic written in dimensionless form read: firings of well-defined bursts of spikes [Figs. 1(c) and 1(d)], or chaotic firings of spikes and bursts of x˙ = y +3x2 − x3 − z + I, (1) spikes [Figs. 1(f) and 1(e)]. Most of these dynam- Int. J. Bifurcation Chaos 2007.17:3071-3083. Downloaded from www.worldscientific.com 2 ical behaviors being oscillatory, they can be char- y˙ =1− 5x − y, (2) acterized by means of the time intervals between 8 consecutive peaks, Ti (i =1, 2,...,N), for each z˙ = r 4 x + − z . (3) 5 function x(t). In neurobiology, these time inter- vals, Ti, are known as inter-spike intervals, and it is The other two dynamical variables, y(t)andz(t), believed that in the structure of inter-spike intervals describe the exchange of ions through the neuron is where neurons encode the information [Sejnowski, by SOUTH CHINA UNIVERSITY OF TECHNOLOGY on 01/01/19. Re-use and distribution is strictly not permitted, except for Open Access articles. membrane by means of fast and slow ion channels, 1995; Abeles, 2004]. Therefore, they are the relevant respectively. The main parameters of the model are observables for neuronal dynamics; because of this, the current that enters the neuron, I,andtheeffi- they will be our basic observables here. ciency of the slow channels to exchange ions, r. We have used them to construct one- The dynamics that one can observe for the dimensional bifurcation diagrams as those pre- action potential, x(t), are quite diverse as illus- sented in Fig. 2. These have been obtained through trated in Fig. 1. There are equilibrium solutions the numerical integration of the equations of where the action potential decays to a constant motion, Eqs. (1)–(3), by means of a fourth-order value, as shown in Fig. 1(a), as well as a variety of Runge–Kutta algorithm with time step 0.005. The Complex Bifurcation Structures 3073 (a) (b) Fig. 2. Two examples of bifurcation diagrams computed for different bifurcation parameters: (a) for I changing and r fixed (r =0.003), and (b) for r changing and I fixed (I =3.25). A vertical dashed line signals the point where the continuous interior crisis occurs, and vertical dotted lines separate the blocks, identified by its periodicity number, p. For (b) only a selected set of blocks of low periodicity have been signaled to avoid having the figure cluttered up with dotted lines. value of one of the system parameters, r or I,was bursts of spikes are separated by lapses of qui- fixed, and time series solutions were obtained for a escence [Fig. 1(e)]. The dynamics in the spiking set of different values of the other parameter, which regime is characterized by one time scale, that of is considered a bifurcation parameter. Then, plot- the spikes, while in the bursting regime there are ting as dots the different values of Ti obtained for two time scales, one for the bursts and other for the each of the values given to the bifurcation param- spikes. The transition between these two dynami- eter, the bifurcation diagrams were obtained. We cal regimes is what is called a continuous interior will note that the conclusions that follow would crisis. For a detailed qualitative and quantitative had been the same if more conventional observables study of the these crisis the reader is referred to to construct the bifurcation diagrams, such as the [Gonz´alez-Miranda, 2003]. maxima of x(t) or the times of crossing a surface in Block structured dynamics is observed to the phase space, had been used. left of the bifurcation diagram, for 1.28 ≤ I ≤ 3.31. Representative results of what is obtained for In this case the dynamical behaviors available can fixed r, and taking I as bifurcation parameter be classified in blocks accordingly to its period- appear in Fig. 2(a). In this case, the value of r is icity, p.
Load more

Recommended publications
  • PHY411 Lecture Notes Part 4
    PHY411 Lecture notes Part 4 Alice Quillen February 6, 2019 Contents 0.1 Introduction . 2 1 Bifurcations of one-dimensional dynamical systems 2 1.1 Saddle-node bifurcation . 2 1.1.1 Example of a saddle-node bifurcation . 4 1.1.2 Another example . 6 1.2 Pitchfork bifurcations . 7 1.3 Trans-critical bifurcations . 10 1.4 Imperfect bifurcations . 10 1.5 Relation to the fixed points of a simple Hamiltonian system . 13 2 Iteratively applied maps 14 2.1 Cobweb plots . 14 2.2 Stability of a fixed point . 16 2.3 The Logistic map . 16 2.4 Two-cycles and period doubling . 17 2.5 Sarkovskii's Theorem and Ordering of periodic orbits . 22 2.6 A Cantor set for r > 4.............................. 24 3 Lyapunov exponents 26 3.1 The Tent Map . 28 3.2 Computing the Lyapunov exponent for a map . 28 3.3 The Maximum Lyapunov Exponent . 29 3.4 Numerical Computation of the Maximal Lyapunov Exponent . 30 3.5 Indicators related to the Lyapunov exponent . 32 1 0.1 Introduction For bifurcations and maps we are following early and late chapters in the lovely book by Steven Strogatz (1994) called `Non-linear Dynamics and Chaos' and the extremely clear book by Richard A. Holmgren (1994) called `A First Course in Discrete Dynamical Systems'. On Lyapunov exponents, we include some notes from Allesandro Morbidelli's book `Modern Celestial Mechanics, Aspects of Solar System Dynamics.' In future I would like to add more examples from the book called Bifurcations in Hamiltonian systems (Broer et al.). Renormalization in logistic map is lacking.
    [Show full text]
  • Synchronization in Nonlinear Systems and Networks
    Synchronization in Nonlinear Systems and Networks Yuri Maistrenko E-mail: [email protected] you can find me in the room EW 632, Wednesday 13:00-14:00 Lecture 5-6 30.11, 07.12.2011 1 Attractor Attractor A is a limiting set in phase space, towards which a dynamical system evolves over time. This limiting set A can be: 1) point (equilibrium) 2) curve (periodic orbit) 3) torus (quasiperiodic orbit ) 4) fractal (strange attractor = CHAOS) Attractor is a closed set with the following properties: S. Strogatz LORENTZ ATTRACTOR (1963) butterfly effect a trajectory in the phase space The Lorenz attractor is generated by the system of 3 differential equations dx/dt= -10x +10y dy/dt= 28x -y -xz dz/dt= -8/3z +xy. ROSSLER ATTRACTOR (1976) A trajectory of the Rossler system, t=250 What can we learn from the two exemplary 3-dimensional flow? If a flow is locally unstable in each point but globally bounded, any open ball of initial points will be stretched out and then folded back. If the equilibria are hyperbolic, the trajectory will be attracted along some eigen-directions and ejected along others. Reducing to discrete dynamics. Lorenz map Lorenz attractor Continues dynamics . Variable z(t) x Lorenz one-dimensional map Poincare section and Poincare return map Rossler attractor Rossler one-dimensional map Tent map and logistic map How common is chaos in dynamical systems? To answer the question, we need discrete dynamical systems given by one-dimensional maps Simplest examples of chaotic maps xn1 f (xn ), n 0, 1, 2,..
    [Show full text]
  • Maps, Chaos, and Fractals
    MATH305 Summer Research Project 2006-2007 Maps, Chaos, and Fractals Phillips Williams Department of Mathematics and Statistics University of Canterbury Maps, Chaos, and Fractals Phillipa Williams* MATH305 Mathematics Project University of Canterbury 9 February 2007 Abstract The behaviour and properties of one-dimensional discrete mappings are explored by writing Matlab code to iterate mappings and draw graphs. Fixed points, periodic orbits, and bifurcations are described and chaos is introduced using the logistic map. Symbolic dynamics are used to show that the doubling map and the logistic map have the properties of chaos. The significance of a period-3 orbit is examined and the concept of universality is introduced. Finally the Cantor Set provides a brief example of the use of iterative processes to generate fractals. *supervised by Dr. Alex James, University of Canterbury. 1 Introduction Devaney [1992] describes dynamical systems as "the branch of mathematics that attempts to describe processes in motion)) . Dynamical systems are mathematical models of systems that change with time and can be used to model either discrete or continuous processes. Contin­ uous dynamical systems e.g. mechanical systems, chemical kinetics, or electric circuits can be modeled by differential equations. Discrete dynamical systems are physical systems that involve discrete time intervals, e.g. certain types of population growth, daily fluctuations in the stock market, the spread of cases of infectious diseases, and loans (or deposits) where interest is compounded at fixed intervals. Discrete dynamical systems can be modeled by iterative maps. This project considers one-dimensional discrete dynamical systems. In the first section, the behaviour and properties of one-dimensional maps are examined using both analytical and graphical methods.
    [Show full text]
  • Lecture 10: 1-D Maps, Lorenz Map, Logistic Map, Sine Map, Period
    Lecture notes #10 Nonlinear Dynamics YFX1520 Lecture 10: 1-D maps, Lorenz map, Logistic map, sine map, period doubling bifurcation, tangent bifurcation, tran- sient and intermittent chaos in maps, orbit diagram (or Feigenbaum diagram), Feigenbaum constants, universals of unimodal maps, universal route to chaos Contents 1 Lorenz map 2 1.1 Cobweb diagram and map iterates . .2 1.2 Comparison of fixed point x∗ in 1-D continuous-time systems and 1-D discrete-time maps .3 1.3 Period-p orbit and stability of period-p points . .4 2 1-D maps, a proper introduction 6 3 Logistic map 6 3.1 Lyapunov exponent . .7 3.2 Bifurcation analysis and period doubling bifurcation . .8 3.3 Orbit diagram . 13 3.4 Tangent bifurcation and odd number period-p points . 14 4 Sine map and universality of period doubling 15 5 Universal route to chaos 17 Handout: Orbit diagram of the Logistic map D. Kartofelev 1/17 K As of August 7, 2021 Lecture notes #10 Nonlinear Dynamics YFX1520 1 Lorenz map In this lecture we continue to study the possibility that the Lorenz attractor might be long-term periodic. As in previous lecture, we use the one-dimensional Lorenz map in the form zn+1 = f(zn); (1) where f was incorrectly assumed to be a continuous function, to gain insight into the continuous time three- dimensional flow of the Lorenz attractor. 1.1 Cobweb diagram and map iterates The cobweb diagram (also called the cobweb plot) introduced in previous lecture is a graphical way of thinking about and determining the iterates of maps including the Lorenz map, see Fig.
    [Show full text]
  • Pseudo-Random Number Generator Based on Logistic Chaotic System
    entropy Article Pseudo-Random Number Generator Based on Logistic Chaotic System Luyao Wang and Hai Cheng * Electronic Engineering College, Heilongjiang University, Harbin 150080, China; [email protected] * Correspondence: [email protected] Received: 23 August 2019; Accepted: 27 September 2019; Published: 30 September 2019 Abstract: In recent years, a chaotic system is considered as an important pseudo-random source to pseudo-random number generators (PRNGs). This paper proposes a PRNG based on a modified logistic chaotic system. This chaotic system with fixed system parameters is convergent and its chaotic behavior is analyzed and proved. In order to improve the complexity and randomness of modified PRNGs, the chaotic system parameter denoted by floating point numbers generated by the chaotic system is confused and rearranged to increase its key space and reduce the possibility of an exhaustive attack. It is hard to speculate on the pseudo-random number by chaotic behavior because there is no statistical characteristics and infer the pseudo-random number generated by chaotic behavior. The system parameters of the next chaotic system are related to the chaotic values generated by the previous ones, which makes the PRNG generate enough results. By confusing and rearranging the output sequence, the system parameters of the previous time cannot be gotten from the next time which ensures the security. The analysis shows that the pseudo-random sequence generated by this method has perfect randomness, cryptographic properties and can pass the statistical tests. Keywords: logistic chaotic system; PRNG; Pseudo-random number sequence 1. Introduction With the rapid development of communication technology and the wide use of the Internet and mobile networks, people pay more and more attention to information security.
    [Show full text]
  • Visual Analysis of Nonlinear Dynamical Systems: Chaos, Fractals, Self-Similarity and the Limits of Prediction
    systems Communication Visual Analysis of Nonlinear Dynamical Systems: Chaos, Fractals, Self-Similarity and the Limits of Prediction Geoff Boeing Department of City and Regional Planning, University of California, Berkeley, CA 94720, USA; [email protected]; Tel.: +1-510-642-6000 Academic Editor: Ockie Bosch Received: 7 September 2016; Accepted: 7 November 2016; Published: 13 November 2016 Abstract: Nearly all nontrivial real-world systems are nonlinear dynamical systems. Chaos describes certain nonlinear dynamical systems that have a very sensitive dependence on initial conditions. Chaotic systems are always deterministic and may be very simple, yet they produce completely unpredictable and divergent behavior. Systems of nonlinear equations are difficult to solve analytically, and scientists have relied heavily on visual and qualitative approaches to discover and analyze the dynamics of nonlinearity. Indeed, few fields have drawn as heavily from visualization methods for their seminal innovations: from strange attractors, to bifurcation diagrams, to cobweb plots, to phase diagrams and embedding. Although the social sciences are increasingly studying these types of systems, seminal concepts remain murky or loosely adopted. This article has three aims. First, it argues for several visualization methods to critically analyze and understand the behavior of nonlinear dynamical systems. Second, it uses these visualizations to introduce the foundations of nonlinear dynamics, chaos, fractals, self-similarity and the limits of prediction. Finally, it presents Pynamical, an open-source Python package to easily visualize and explore nonlinear dynamical systems’ behavior. Keywords: visualization; nonlinear dynamics; chaos; fractal; attractor; bifurcation; dynamical systems; prediction; python; logistic map 1. Introduction Chaos theory is a branch of mathematics that deals with nonlinear dynamical systems.
    [Show full text]
  • Notes on Bifurcations and the Logistic
    PHY256 Lecture notes on Bifurcations and Maps Alice Quillen January 30, 2021 Contents 0.1 Introduction . 2 1 Bifurcations of one-dimensional dynamical systems 2 1.1 Saddle-node bifurcation . 2 1.1.1 Example of a saddle-node bifurcation . 4 1.1.2 Another example . 6 1.2 Pitchfork bifurcations . 7 1.3 Trans-critical bifurcations . 10 1.4 Imperfect bifurcations . 10 1.5 Relation to the fixed points of a simple Hamiltonian system . 13 2 Iteratively applied maps 14 2.1 Cobweb plots . 14 2.2 Stability of a fixed point . 16 2.3 The Logistic map . 16 2.4 Two-cycles and period doubling . 17 2.5 Sarkovskii's Theorem and Ordering of periodic orbits . 22 2.6 A Cantor set for r > 4.............................. 24 3 Lyapunov exponents 26 3.1 The Tent Map . 28 3.2 Computing the Lyapunov exponent for a map . 28 3.3 Entropy . 29 3.4 The Maximum Lyapunov Exponent . 29 3.5 Numerical Computation of the Maximal Lyapunov Exponent . 31 3.6 Indicators related to the Lyapunov exponent . 32 1 0.1 Introduction For bifurcations and maps we are following early and late chapters in the lovely book by Steven Strogatz (1994) called `Non-linear Dynamics and Chaos' and the extremely clear book by Richard A. Holmgren (1994) called `A First Course in Discrete Dynamical Systems'. On Lyapunov exponents, we include some notes from Allesandro Morbidelli's book `Modern Celestial Mechanics, Aspects of Solar System Dynamics.' In future I would like to add more examples from the book called Bifurcations in Hamiltonian systems (Broer et al.).
    [Show full text]
  • Characteristics of Complexity in Selected Economic Models in the Light of Nonlinear Dynamics A
    Vol. 123 (2013) ACTA PHYSICA POLONICA A No. 3 Proceedings of the 6th Polish Symposium of Physics in Economy and Social Sciences (FENS2012), Gda«sk, Poland Characteristics of Complexity in Selected Economic Models in the Light of Nonlinear Dynamics A. Jakimowicz Department of Quantitative Methods, Faculty of Economic Sciences, University of Warmia and Mazury in Olsztyn M. Oczapowskiego 4, 10-719 Olsztyn, Poland The catastrophe theory and deterministic chaos constitute the basic elements of economic complexity. Elemen- tary catastrophes were the rst remarkable form of nonlinear, topological complexity that were thoroughly studied in economics. Another type of catastrophe is the complexity catastrophe, namely an increase in the complexity of a system beyond a certain threshold which marks the beginning of a decrease in a system's adaptive capacity. As far as the ability to survive is concerned, complex adaptive systems should function within the range of optimal complexity which is neither too low or too high. Deterministic chaos and other types of complexity follow from the catastrophe theory. In general, chaos is seemingly random behavior of a deterministic system which stems from its high sensitivity to the initial condition. The theory of nonlinear dynamical systems, which unites various man- ifestations of complexity into one integrated system, runs contrary to the assumption that markets and economies spontaneously strive for a state of equilibrium. The opposite applies: their complexity seems to grow due to the inuence of classical economic laws. DOI: 10.12693/APhysPolA.123.542 PACS: 89.65.Gh, 05.45.Pq, 05.45.−a, 89.75.−k 1. Introduction the Marxist convention, economy was divided into two sectors: the consumer goods sector and the capital goods The denition of complexity proposed by Day is popu- sector.
    [Show full text]
  • Transcritical Bifurcation
    Bifurcation and chaos Bifurcation and chaos Outline Outline of Topics What is bifurcation? Bifurcation and chaos Some concepts Bifurcation examples in MATLAB Shan He What is chaos School for Computational Science Some concepts about chaos University of Birmingham Chaos examples in MATLAB Module 06-23836: Computational Modelling with MATLAB MATLAB toolboxes Assignment Bifurcation and chaos Bifurcation and chaos What is bifurcation? What is bifurcation? Some concepts Some concepts What is a bifurcation? Classification of bifurcations ◮ Local bifurcations : a parameter change causes the stability of an equilibrium to change. Including: ◮ Bifurcation : a small smooth change of some parameter ◮ Saddle-node (fold) bifurcation values (the bifurcation parameters) of a system causes a ◮ Transcritical bifurcation sudden ‘qualitative’ or topological change in its behaviour ◮ Pitchfork bifurcation ◮ Bifurcations occur in both continuous systems, e.g., ODE and ◮ Hopf bifurcation discrete systems. ◮ Period-doubling (flip) bifurcation ◮ Codimension : the number of parameters which must be ◮ Global bifurcations : occurs when ‘larger’ invariant sets, such varied for the bifurcation to occur. as periodic orbits, collide with equilibria. Cannot be detected purely by a stability analysis of the equilibria. ◮ We will focus on local bifurcations in this lecture. Bifurcation and chaos Bifurcation and chaos What is bifurcation? What is bifurcation? Bifurcation examples in MATLAB Bifurcation examples in MATLAB Example: Transcritical bifurcation Example: Saddle-node bifurcation ◮ Local bifurcations. ◮ Local bifurcations. ◮ There is always at least a fixed point exists for all values of a ◮ parameter and is never destroyed. Also known as tangential bifurcation or fold bifurcation. ◮ ◮ A fixed point interchanges its stability with another fixed Two equilibria collide and annihilate each other.
    [Show full text]
  • Variations of the Lorenz-96 Model
    Variations of the Lorenz-96 Model Master Thesis in Mathematics: Mathematics and Complex Dynamical Systems Name: Anouk F.G. Pelzer, s2666545 First supervisor: Dr. A.E. Sterk Second supervisor: Prof. Dr. H. Waalkens Date: 29 June 2020 Abstract. In this thesis we will investigate the differences between the monoscale Lorenz-96 model and its modifications. We obtain these modifications by changing the structure of the nonlinear terms in the original Lorenz-96 model. We will treat the gen- eral modified model and three specific systems and compare these with the Lorenz-96 model. To determine the dynamics of the models, we will study the eigenvalues of the Jacobian matrix at the trivial equilibrium, Lyapunov coefficients to distinguish between sub- and supercritical Hopf bifurcations, Lyapunov exponents to determine when there is chaos for example etc. Some of the results are that in the Lorenz-96 model there are no escaping orbits, while this is only true under some conditions for the modified systems. Furthermore there are differences in bifurcations. The external forcing F ap- pearing in the equations of all these models can be used as a bifurcation parameter. The trivial equilibrium is always stable when F is zero for every model. For F < 0 some modifications has a stable trivial equilibrium, while this is not the case for the original model. For this model there only occur first Hopf bifurcations when F is positive, but for its modifications there can be other (first) bifurcations too, like a Pitchfork bifurcation. There are even bifurcations occuring for these modified systems, while these don't ap- pear in the original Lorenz-96 model case, such as degenerate bifurcations meaning that suddenly there appear simultaneously more than one equilibrium and two eigenvalues of the Jacobian matrix are zero at the same bifurcation parameter F .
    [Show full text]
  • A Two-Parameter Modified Logistic Map and Its Application to Random
    S S symmetry Article A Two-Parameter Modified Logistic Map and Its Application to Random Bit Generation Lazaros Moysis 1 , Aleksandra Tutueva 2 , Christos Volos 1,* , Denis Butusov 3, Jesus M. Munoz-Pacheco 4 and Hector Nistazakis 5 1 Laboratory of Nonlinear Systems, Circuits & Complexity (LaNSCom), Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece; [email protected] 2 Department of Computer-Aided Design, Saint Petersburg Electrotechnical University “LETI”, 5, Professora Popova st., 197376 Saint Petersburg, Russia; [email protected] 3 Youth Research Institute, Saint-Petersburg Electrotechnical University “LETI”, 5, Professora Popova st., 197376 Saint Petersburg, Russia; [email protected] 4 Faculty of Electronics Sciences, Autonomous University of Puebla, Puebla 72000, Mexico; [email protected] 5 Section of Electronic Physics, Department of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece; [email protected] * Correspondence: [email protected] Received: 20 April 2020; Accepted: 8 May 2020; Published: 18 May 2020 Abstract: This work proposes a modified logistic map based on the system previously proposed by Han in 2019. The constructed map exhibits interesting chaos related phenomena like antimonotonicity, crisis, and coexisting attractors. In addition, the Lyapunov exponent of the map can achieve higher values, so the behavior of the proposed map is overall more complex compared to the original. The map is then successfully applied to the problem of random bit generation using techniques like the comparison between maps, XOR, and bit reversal. The proposed algorithm passes all the NIST tests, shows good correlation characteristics, and has a high key space. Keywords: random bit generation; logistic map; chaos; chaos-based cryptography 1.
    [Show full text]
  • Dynamics of the Lorenz-96 Model Van Kekem, Dirk Leendert
    University of Groningen Dynamics of the Lorenz-96 model van Kekem, Dirk Leendert IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2018 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): van Kekem, D. L. (2018). Dynamics of the Lorenz-96 model: Bifurcations, symmetries and waves. Rijksuniversiteit Groningen. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license. More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne- amendment. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 06-10-2021 1 INTRODUCTION The relevance of mathematically defined systems cannot be too “ strongly emphasized; much of what we know, or believe that we know, about real systems has come from the study of models.
    [Show full text]